1. Field of Invention
This invention relates to an electrostatic chuck used for holding articles such as semiconductor wafers, dielectric substrates, panel displays and the like during processing and, in particular, to such a chuck employing thermoelectric heating or cooling.
2. Description of the Prior Art
There are known techniques for applying heat to an electrostatic chuck and in turn to a wafer clamped thereon during semiconductor processing.
Niori, et al, U.S. Pat. No. 5,280,156 describes an electrostatic chuck whose ceramic substrate or body has a heat generating element embedded therein. The heat generating element is energized to heat a wafer-attracting surface of the chuck to a desired temperature which in turn can heat a wafer positioned thereon uniformly.
Kawada, et al, U.S. Pat. No. 5,556,043 relates to a ceramic electrostatic chuck, with built-in heater, the heater being a heat generating layer made from an electrostatic ceramic. Other electrostatic chuck U.S. patents with heat generating layers are: Kawada, et al, U.S. Pat. No. 5,606,484; Kawada, et al, U.S. Pat. No. 5,663,865; and, Kawada, et al, U.S. Pat. No. 5,665,260.
Also known are various techniques for wafer cooling during semiconductor processing.
In Jones, et al, U.S. Pat. No. 4,194,233 an inert gas is used to conduct away the heat normally produced during processing.
Lewin, et al, U.S. Pat. No. 4,502,094 discloses an electrostatic chuck in which temperature variations across the semiconductor wafer are minimized by the use of a plurality of closely spaced conductor pillows in contact with the wafer and extending therefrom to a heat sink.
In U.S. Pat. No. 4,645,218 to Ooshio, et al, the chuck body is provided with a plurality of channels for passing a cooling medium there through in order to cool the wafers.
Logan, et al, U.S. Pat. Nos. 5,155,652 and 5,191,506, utilize heat sinks with backside cooling.
The large volume of liquid involved in prior art cooling for electrostatic chucks creates a large thermal mass whose temperature cannot be changed rapidly.
Thermoelectric units have been thought of before for use in semiconductor process equipment.
Wright, et al, U.S. Pat. No. 5,584,183 pertains to a thermoelectric exchange for transferring heat between two fluids, as in semiconductor process equipment.